Key fob not recognized

I just replaced the battery on the key fob for my wifes 2007 prius. This morning she went to leave and the car wouldnt start even when the key was inserted. The battery on the remote is good it will lock unlock and panic as well as the red light on the fob lights up. Before today the car car would start with fob inserted. On the dash it displays the key not detected light both inside the car and when fob is inserted